Smoking has been labeled as a leading cause of preventable death in the United States. As such a great deal of effort has been devoted to encouraging cessation among established smokers and discouraging smoking uptake among youth in the U.S. population. It is important that resources devoted to these tasks produce the desired results. The greatest possible understanding of the behavioral processes of smoking cessation and smoking uptake is essential to the refinement of existing and the development of new interventions aimed at encouraging cessation and preventing uptake. A great deal of data about smoking behavior is available from both national and state level population surveys and data bases. Proposed investigations include: Identification of factors related to successful cessation among callers to the California Smokers' Helpline, identification of the characteristics of established adolescent smokers who make quit attempts and who are successful, and further validation of the measure of susceptibility to smoking and identification of the factors associated with progression from earlier to more advanced stages in the uptake process using longitudinal data. In addition, the evaluation of specific population interventions is important to both justify their continuation and the widening of their reach. We propose to use available data to determine whether associations exist between per capita cigarette consumption and the institution of various population-based interventions (e.g., increased cigarette taxes, ordinances regarding smoking in the work place, the ASSIST program ) to discourage smoking. These studies should complement those of the other smoking related projects as the results may relate to the design of specific interventions both in adults and youth that will ultimately increase the number of nonsmokers in the population.